Hi there, I just hit the same issue. What makes this a really unhappy problem is that, in addition to disk space and the possible issues at reboot, another resource that seems to be consumed by this is system memory. Once I hit this issue, my computer start swapping and the desktop becomes mostly unusable. I assume ext4 tries to keep much of the directory information for /tmp in memory... Kudos to it for not crashing, but at the same time it's a puzzling problem to track down, since the memory is gone, but not attributable to any running process.
Andreas
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